WO-A-02/34653 shows such an excavating device. The described excavating device uses a jet of fluid under pressure in which abrasive particles are mixed to erode the material of a surface in order to generate a hole in said surface. The jet is placed under an angle relative to the advancement direction of the excavating device in the hole, and is rotatably operated inside the hole in order to create the hole. This is shown to result in a hole with a heap-shaped center part on the bottom of the hole, as a result of the rotation of the abrasive jet.
The excavating device according to the prior art comprises a distance holder in the form of an L-shaped bracket, in order to ensure a pre-determined distance of the nozzle to the bottom of the hole. The bracket contacts the hole bottom surface in the part of the hole bottom surface that is diametrically opposed to where the abrasive jet stream impacts the hole at that very moment. When the abrasive jet leaves the nozzle outlet it enters a free space.
This may lead to misalignment of the abrasive jet stream, and thereby undesired erosion into the bore hole wall, and a less effective use of the abrasive jet and the energy contained therein.